5 Structure and function of blood vessels Flashcards
All blood vessel must be….
resilient and flexible so they can stay open during movement
What is the structure of all vessels but capillaries?
- Lumen
- Tunica interna
- Tunica media
- Tunica adventitia
Structure of tunica interna
- basal lamina (epithelia)
- squamous epithelial layer
- sub-epithelial connective tissue (dense regular)
Structure of tunica media
- loose connective tissue (containing some smooth muscle fibres)
- Elastic fibres
- also known as the muscular layer
Structure of tunica adventitia
- can contain vaso vasorum
- contains CT that merges with surrounding CT
When an artery is compared to its corresponding vein what are the differences?
- Artery lumen appears smaller
- Thicker walls
- No valves
- Is more resilient (doesn’t lose its shape)
Types of arteries:
Elastic/conducting
Muscular/Distributing
Arterioles/Resistive
Elastic conducting arteries consist of:
What do they do?
Aorta, Carotid, Bracheophalic
-conduct blood from the heart so need to be able to withstand changes in pressure
Structure of elastic arteries:
- Large tunica media
- Tunica adventitia
- Lots of elastic fibres
- Not much smooth muscle
- 2.5 cm in diameter
Muscular arteries:
(distributing)
- most named arteries (e.g. femoral)
- Control speed of blood tailored to organs needs
Muscular artery structure
- 0.5mm-0.4cm diameter
- tunica media has lots of smooth muscle
- thick adventitia
- can vasoconstrict and dilate
Arterioles structure:
- virtually no adventitia
- can vasoconstrict and dilate
- less than 30 micrometers diameter
- 1 or two layers of smooth muscle in media
Arterioles function:
- controls blood flow to organs
- responsible for blood pressure
- can vaso constrict or dilate
what is the diameter of capillaries?
8 micrometers
What are the three types of capillary?
- sinusoidal
- continuous
- fenestrated
Sinusoidal capillaries:
- have holes in the epithelial layer
- incomplete or missing basal lamina
- for exchange of plasma proteins e.g. RBCs
- lined by specialised cells e.g. in the liver where phagocytes engulf RBCs
Continous capillaries:
- Most are these
- No gaps between epithelial cells
- found in lungs etc for gas exchange and skeletal muscle
Fenestrated capillaries:
-Have small gaps between epithelial cells
-Contain fenestrations/pores
for rapid exchange of molecules (and some small proteins)
-Found in the kidney (glomerulus) and endocrine glands
What are the main features of capillary beds?
- Metarteriole
- arteriovenous anastamosis
- pre capillary sphyncters
What is a metarteriole?
A continuous vessel linking artery and venous blood supply with many capillaries branching off it
-restricting the blood flow to this can decrease it to the whole capillary bed
What is an arteriovenous anastamosis?
A continuous vessel linking artery and venous blood supply with no capillaries branching off it
-blood flow through here can bypass the capillary beds
Venules:
function
size
structure
- collect blood from capillary beds and deliver it to small veins
- tunica adventitia is predominant
- very thin walls with essentially just epithelia and basal lamina
- diameter varies around 20 micrometers
- as they get larger you get more smooth muscle in the walls
Veins sizes
small - less than 2mm
medium - 2-9mm
large - more than 9 mm
Which have higher pressure capillaries or veins?
Capillaries
